(1) Field of the Invention
The present invention relates to the field of information display technology for electronic devices. Specifically, the present invention relates to a display component capable of use within a computer system.
(2) Prior Art
Flat panel displays or liquid crystal displays (LCDs) are popular display devices for conveying information generated by a computer system. The decreased weight and size of a flat panel display greatly increases its versatility over a cathode ray tube (CRT) display. High quality flat panel displays are typically back-lit. That is, a source of illumination is placed behind the LCD layers so that visualization of the resultant image is made much easier. However, providing a back-lit screen generally makes the display screen non-transparent. It is desired, then, to provide a LCD screen having the high quality image generation characteristics of a back-lit LCD, yet offering a transparent LCD screen. The present invention provides such advantageous capability.
During meetings and lectures, overhead projection units or "projectors" are often used to project transparent slides, foils or "overheads" onto a screen or wall. The projection and resultant enlargement of these images onto the screen allows image presentation to a large audience. With the introduction of computer systems that offer a wide range of software, including graphics packages and slide presentation capabilities, it would be advantageous to allow the graphic image output of a computer system to be projected and enlarged onto a screen for audience presentation. The present invention offers such advantageous capability.
Further, some back-lit LCD screens utilize light extraction patterns. These screens have lamps along the edges of a light pipe and depend on an extraction pattern to distribute the light intensity. The light extraction patterns of the prior art are uni-directional in that the dots vary in size only in one direction, depending on their distance from the lamp in that dimension only. As a result, in prior art back-lit displays that utilize light extraction patterns, edges and corners are often darker and the overall image is not uniformly bright. This condition requires that lights longer than the active area be used to account for the nonuniformity. It would be advantageous to provide acceptable uniform illumination of the LCD screen using lights of lower intensity (and shorter length) for power conservation. The present invention provides such advantageous functionality.
Accordingly, it is an object of the present invention to improve the versatility of a flat panel display screen. It is an object of the present invention to provide an improved flat panel display screen that can be used with an overhead projector. It is also an object of the present invention to provide a direct view flat panel display screen that is back-lit that can also be used with an overhead projector to project and enlarge a resultant display image. It is yet an other object of the present invention to provide such capability in a portable computer system or a display subsystem wherein the back-lighting components of the display subsystem are removable, thus exposing a transparent LCD screen for use in combination with the overhead projector. It is yet another object of the present invention to provide a removable door assembly as discussed above wherein the illumination sources remain within the display subsystem unit when the door assembly is removed. These, and other objects of the present invention not specifically mentioned above, will become clearer within discussions of the present invention herein.